The present invention relates to a vibrating device having an axially driven movable member, and more particularly to a vibrating device mounted in a portable telephone for signaling a user by vibration of the movable member.
In recent years, there is popularized various portable instruments such as portable telephone, PDA (Personal Digital Assistant), wearable computing instruments and so forth. In these instruments, vibrating devices are mounted for informing signals, by vibration without producing sounds.
FIG. 6 is a perspective view showing a conventional vibration device disclosed in Japanese Patent Laid Open 7-107699. A direct current motor 131 has a rotating shaft 136 supported by a bearing 133. There is formed an annular groove 135 on which an eccentric weight 134 is secured by a fixer 140.
In such a motor, since a commutator and a brush assembly are provided, or manufacturing cost increases. It takes a time before the rotating speed approaches 7000xcx9c8000 rpm. Therefore, the device is improper to a device which vibrates in accordance with a music signal. Furthermore, arcs generated between the commutator and brushes cause the quality and the life of the motor to reduce.
An object of the present invention is to provide a vibrating device which may be manufactured at a low cost and has a high performance.
According to the present invention, there is provided a vibrating device comprising an axially elongated frame, a hollow yoke having an axially elongated shape and an opening at an end thereof, and axially movably provided in the frame, a cylindrical permanent magnet securely provided in the yoke, a coil bobbin cantilevered in the frame and having an end portion inserted in the yoke from the opening and in a space between the yoke and the permanent magnet, a driving coil mounted on the coil bobbin, at least one coil spring provided for resiliently holding the yoke in the frame.
The yoke has a hollow cylindrical form, and the yoke has a cup shape.
At least one weight is secured to a bottom of the yoke.
A plurality of guide projections are provided on an inside wall of the frame for movably supporting the yoke.
A pole piece made of magnetic material is secured to an end of the permanent magnet.
The device further comprises a plurality of axial grooves in each of which the guide projection is axially movably engaged.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.